Roof Boxes are designed to withstand extreme weather and can take a beating or two but that does not mean that it is invincible. Over the course of time, roof cargo boxes may develop cracks as the sun, wind and rain can take their toll on it. But repairing a cracked roof box is that complicated. In fact, it can be done in just seven easy steps.
Sand The Damaged Area
You’ll need to sand the damaged area down until it is smooth but not too smooth. Epoxy and other sealants can become weak over time if the area is too smooth, so it’s important to strike a fine balance. Too much sanding and you’ll end up with an uneven surface that will be difficult to paint or stain; too little sanding and the area could remain vulnerable to future damage. Try to use 80 grit sandpaper. The grit of the sandpaper should be just rough enough to remove the rust but not so gritty that it will damage the underlying material.
Clean The Area
Alcohol wipes are perfect for cleaning surfaces before painting or staining. If you don’t have any alcohol wipes on hand, a clean cloth soaked in rubbing alcohol will work just as well.
Clean surface is a must here because unclean surface will make it harder for the paint or stain to adhere properly.
Frame-Treating the Plastic
After you’ve cleaned and sanded the area, it’s important to flame-treat the plastic. Use a propane torch to heat the plastic. You have to be extremely careful while heat-treating the plastic with a propane torch. Pass the flame over the surface of the plastic fast enough that the plastic turns a glossy black. If the flame lingers in one spot for too long, it will cause the plastic to melt.
The surface gets oxidized when it is heated with the flame. This helps the paint or sealant to adhere better to the surface.
Warm Things Up
Before you mix the hardener and resin, you need to make sure that you have heated everything up. To bring down the viscosity of the epoxy, you need to heat the resin and the hardener otherwise epoxy will not be able to get deeper into the cracks and will not form a strong bond. The damaged area also needs to be heated properly with a heat gun but make sure that you are not heating it to the point of melting. That would do more harm than good. You can even use a hairdryer for the same purpose if you don’t have a heat gun.
Mix Epoxy Carefully
Now, it is the time to commix small amount of flex epoxy. Mix it properly. No need to rush. Thankfully, G/flex is easy to use. All you need to do is to maintain 1:1 ratio of hardener and resin. 45 minutes pot life is more than enough for most of us to do the repairing work. If you are working in warmer climates, then you should be careful as the epoxy will cure faster.
First use a syringe to apply epoxy into the cracks. You don’t need to use too much epoxy, just enough to fill the cracks. use a small brush or a mixing stick to help you spread the epoxy evenly. Make sure that the crack is completely filled. You can even use a stick to push the epoxy into the cracks.
Let It Cure
After you have applied the epoxy, let it cure for at least 7 hours. Excess epoxy should be removed before it cures. You can use a clean cloth to do that. If the epoxy is still tacky after 7 hours, then let it cure for longer. Do not try to force the epoxy to cure faster by using a heat gun or hairdryer. This will only damage the epoxy.
You can always use thick flex epoxy and apply on the damaged sections of the roof box for extra strength. Just make sure that you don’t use too much epoxy or it will start to drip. Use it like a filler and it will help to add extra strength to the roof box. Want to it beef up further? Well, try adding some fibreglass fabric and it will add more strength to the roof box.
First apply a fresh coating of flex 650 epoxy on that damaged section and then place that fibreglass fabric on that wet surface. Use a plastic spreader to remove any bubbles and to flatten that fabric. Wait for an hour or two and then apply another layer of epoxy over the top of that fibreglass fabric.
Let it rest for at least 7 hours before you do anything with that roof box.